Lecture 4 (Chris Allen) Flashcards
1
Q
How does an acid affect the pH of a solution
A
- Increases the hydrogen ion concentration.
- Decreases the hydroxide ion concentration because of the tendency for hydrogen ions to combine with hydroxide ions.
- Therefore the pH value decreases.
2
Q
What is a buffer and how does it work
A
- A buffer is a substance that minimises changes in the concentration of hydrogen and hydroxide ions in a solution.
- It does this by accepting hydrogen ions from the solution when they are in excess and donating hydrogen ions to the solution when they have been depleted.
- Most buffer solutions contain a weak acid and its corresponding base, which combine reversibly with hydrogen ions.
3
Q
What are the basic structural components of an alpha-amino acid
A
- Basic (amine) and acidic (carboxylate) groups which affect properties in water and facilitate polymerisation.
- An R- side chain which can potentially be functionalised do in a variety of ways, allowing proteins to have a vast array of properties.
- Chiral carbon centre.
- One hydrogen atom directly attached to the chiral carbon.
4
Q
What does it mean when pH=pKa
A
An acid is 50% dissociated.
5
Q
When is the pH of a solution most resistant to change
A
When pH=pKa
6
Q
When are buffers most effective
A
When they are with +/- 1 pH unit of their pKa.
7
Q
Which amino acid does not contain a chiral centre
A
Glycine
